Electromagnetic waves cover a spectrum from X-ray to radio frequencies. Among the spectra, the terahertz (“THz”) waves, ranging from 0.1 THz (1012 Hz) to 30 THz, have been a focus of intense research in the last three decades for many promising applications, e.g., spectroscopy, safety surveillance, cancer diagnosis, imaging, and communication.
However, THz applications are limited due to a lack of high performance optical components that include a THz source, a THz detector, a phase shifter, and a modulator. In particular, the phase shifter, used to manipulate degrees of the phase of THz waves, and the modulator, used to change the amplitude of THz waves, are critical to THz applications.
Currently, the THz phase shifter mostly relies on electrically or magnetically controlled devices, either of which presents a major limitation. Namely, a high voltage, i.e., higher than 100 V, is required for an electrically controlled phase shifter and a magnetic field-based phase shifter is difficult for integration due to its bulky magnet(s).
Turning to the THz modulator, it typically suffers from a high insertion loss, i.e., a decrease in the intensity of THz signals. A vanadium oxide based THz modulator, which shows a low insertion loss, needs to be operated at a high temperature.
There is a need to develop a high-performance THz phase shifter and THz modulator for use THz in commercial applications.